I wrote a blog post
on installing the Progressive Industries EMS-HW30C into my fifth wheel if you haven't read it.
Anyway I am at a notoriously bad campground for power issues, many folks have told me stories. Last night I noticed the readout panel showed AC Volts 106! if it had gone down to 103 the unit would have automatically disconnected power.
If I didn't have the readout I would have been oblivious to the low voltage situation. Also the unit shows you your current draw which is nice.
Really liking the unit so far.